Hello all, have the 345 in for some adjustments and we are thinking about an oil change. I just read through Chaplain Kent's awful experience with same - consider myself forewarned! It is at a reputable truck center. Anyway, we have been discussing whether or not to use synthetic oil at this point, 69000 on an 86 345. Any strong feelings either way?

I made the switch to synth with about 10,000 miles more in the engine than you now have.....remember, the 345 is a heavy beast and the 454 COULD give up the ghost at any time - with or without synthetic oil.

Another thing to remember, oil life should be limited by a time interval as well as a mileage interval...a good arguement for Dino oil since it is a whole lot cheaper.

One of the things that caused me concern was the warning that using Synth in an "older" engine could cause some "oil weeping" at marginal seals - didn't have the first leak - but it didn't improve the gas mileage either.

I do run Synthetic in the rear end - was advised to wait until the tranny had about 10,000 miles on it prior to making the switch, but the new Allison trannies now come from the factory with non-Dino installed.

I have used Valvoline synth blend, and now gone back to regular Castrol as an oil "review" I had read rated it very high.
Regular oil changes, proper warm up, regular use and care means a lot also to your 454's longevity.

I run dino oil (Castrol) and just do the oil/filter change every 3000 miles. It's cheap and easy to do yourself. I also know that it's done right and I gets me under there to look at everything.

I've also taken to performing some routine "preventative checks" at each oil change. I pull each plug and check it for burn properties, while the plugs are out I perform a compression check on each cylinder, check the air cleaner, breathers, check the coolant levels, look for oil in the coolant, etc.

A little overkill for an oil change but with 186,000 miles on the coach and who knows how many on the motor it's cheap, simple preventative maintenance that might alert me to a larger issue before it becomes catastrophic.

Of course my wife wonders why it takes me two hours to do an oil change

I also know that it's done right and I gets me under there to look at everything.

Very good idea. Most "oil change techs" probably don't have a clue about anything under a vehicle other than the filter and drain plug, and as Chaplain Kent unfortunately discovered some are just clueless. Unless it is a glaring safety defect I doubt if you would even hear about any problem even if it was noticed. A lot of shops don't want to deal with a vehicle this old or large. If yours is a gas engine it will use a spin on filter, less chance of the wrong part. It is not a fun place to spend time, but one of those jobs that is the price of ownership.

I vote dino oil. Probably more important than the type is the time interval between uses. Even with the best of intentions these engines are not really properly used, they sit for weeks then haul 14,000 lbs. down the road. Daily use is better. Considering the price of synthetic oil and common rv usage, I would rather use cheaper dino oil and keep shorter oil change intervals.

It seems that unless your engine is new or your running it at high temperatures for prolonged periods the price difference would be better spent changing it more often. It's my understanding that if you've been using a standard oil changing to synthetic will cause it to leak past the rings and you'll be burningthat price difference.

I put penzoil synthetic in the jeep at 16k miles and have used it ever since. I change oil and filters every 5k. I have not had any leaks in the seals, but you are susposed to run one oil change interval before switching to synthetic so that the seals will properly seat. Right now the engine has 140 k miles on it. Is it worth the difference in price, no. Would I do it again, yes. Its a 92 jeep that has been garaged its entire life and I am passing it on to my grandson. I run dino in my 92 Cummins and in my 2001 town and country. I doubt that the chrysler will live as long as the jeep. Synthetic for engines that sit unused for long periods as well as cold start-ups.

I run Synthetic ( 100%) in my 5.7l Suburban, and am very happy with the overall result. My engine uses no oil now, ( used to burn a quart every 600miles) and runs quieter and smoother at startup. I use Amsoil, but do not believe in their 25000 mile oil change interval. I change my oil every 6 month or 9000 miles, whichever comes first. I will not go back to dino oil for this vehicle.
I costs me about $ 40.00 in materials, including their HD filter. I find this reasonable, in relation to the improvements that I noticed.
I do believe that it is of advantage, especially in an engine that is used in extra duty service such as towing or motorhome use.
Otherwise, all fresh oil is good oil......

The old 454 cubic inch in the motorhomes is one of the most overworked engines I am aware of and would benefit from the higher operating temperature of synthetic oil. However, if you use it fairly low annual miles, then it is expensive to use Syn. and change it because of time and not distance.There are partial syn oils on the market and they might be a good option for an older motor that works hard but, is changed due to time.